The Digital Subscriber Line (DSL) technology, during all its history, attempted to increase the bit rate in the aim to deliver more broadband services to the customer. Unfortunately, copper loops deployed from the Central Office (CO) to customer premise equipment (CPE, also referred to as CPE devices which are located in the customer's premises) are rather long and do not allow transmission of data with bit rates more than few megabits per second (Mb/s). To increase the bit rates, modern access networks use street cabinets, MDU-cabinets (MDU=multi dwelling unit), and similar arrangements: cabinets are connected to the CO by a high-speed backbone communication line, like multi-gigabit passive optical network (GPON) and installed close to the customer premises. From these cabinets, high-speed DSL systems, such as Very-High-Bit-Rate DSL (VDSL), can be deployed. The current VDSL systems (ITU-T Recommendation G.993.2) have range of operation about one kilometer, providing bit rates in the range of tens of Mb/s. To increase the bit rate of VDSL systems deployed from the cabinet, recent ITU-T Recommendation G.993.5 defined vectored transmission that allows increasing bit rates up to 100 Mb/s per direction.
However, recent trends in the access communications market show that 100 Mb/s is still not sufficient and bit rates up to one gigabit per second (Gb/s) are required. Accordingly, further increase of the bit rate is one design goal for modern DSL systems, wherein bit rates of about 1 Gb/s are desired. This is implemented by bringing a high-capacity fiber into the neighborhood and connecting to this fiber backbone multiple distribution points (DPs), each serving a small customer area, typically of up to 200 meter around.
At each DP a certain number of services for the connected customer premises are branched out from the fiber backbone and conveyed via the copper lines served by the DP to the CPE. These different services branched by the DP out of the fiber backbone may use different communication protocols, such as Ethernet, ATM, UDP, etc. The packets of data received at the DP from the fiber backbone are multiplexed and switched towards particular user CPEs, which are connected to the DP via twisted pair lines. The receiving CPEs are capable to recover each packet of each particular protocol and pass them to the associated application.